Validation of a GEANT4 simulation of neutron stimulated emission computed tomography

Neutron stimulated emission computed tomography (NSECT) is being proposed as a non-invasive technique to detect concentrations of elements in the body for diagnosis of liver iron overload. Several experiments have been conducted to investigate NSECT's ability to determine iron concentration in liver tissue and evaluate the accuracy and sensitivity of the system. While these experiments have been successful in demonstrating NSECT's capability of quantifying iron and other tissue elements in-vivo, they have been prohibitively time consuming, often requiring as much as 24 hour acquisitions for accurate quantification. Such extensive scan times limit the use of the experimental system for initial feasibility testing and optimization. As a practical alternative, GEANT4 simulations are being developed to investigate system optimization and aid further progress of the experimental technique. This work presents results of a validation study comparing the results of a GEANT4 simulation with experimental data obtained from a sample of iron. A simulation of the NSECT system is implemented in GEANT4 and used to acquire a spectrum from a simulated iron sample. Scanning is performed with a 7.5 MeV neutron beam to stimulate gamma emission from iron nuclei. The resulting gamma spectrum is acquired and reconstructed using high-purity germanium (HPGe) detectors and analyzed for energy peaks corresponding to iron. The simulated spectrum is compared with a corresponding experimental spectrum acquired with an identical source-detector-sample configuration. Five peaks are detected corresponding to gamma transitions from iron in both spectra with relative errors ranging from 4.5% to 17% for different peaks. The result validates the GEANT4 simulation as a feasible alternative to perform simulated NSECT experiments using only computational resources.